Anodized aluminum objects can take on bright colors.
Aluminum is a light metal used in many different applications, from cookware to engine parts. Aluminum is also a major component of paintball markers and computer components. Unfortunately, aluminum is reactive and relatively soft. Anodizing increases surface hardness and protects aluminum from corrosion. It can also be used to add color to an aluminum item.
Home anodizing requires some dangerous chemicals and involves electricity. It can be done safely, though. You simply need to observe a few precautions. Always wear safety glasses or goggles and gloves while anodizing. Wear heavy clothes that you don’t mind damaging, or an apron. Perform the anodizing process in a well-ventilated room, away from pets and children. If good ventilation isn’t available, wear a chemical respirator.
Anodizing requires an electrolyte, a dye, a power source and a nonreactive container, such as a plastic storage tub. Battery acid is a common choice for the electrolyte, as it is readily available from the hardware store. Fabric dye or food coloring work to add color to your aluminum parts–just remember to use light-fast dyes if the part will be exposed to sunlight. You can use a 6- to 12-volt battery charger to provide the electric current.
Before anodizing, clean the part thoroughly. Immerse the part in a bath of three tablespoons of lye or 1 to 2 ounces of nitric acid to one gallon of water to remove any contaminants. Fill your container with three parts water and one part battery acid. Never add water to acid–the reaction could be dangerous. Suspend an aluminum plate and the part in the electrolyte. Hook the negative lead of the battery charger to the plate and the positive lead to the aluminum part.
Turn on the battery charger. Use a rating of at least two volts. More current will produce a stronger effect and anodize more quickly. You should see bubbles or a white fog coming off of the aluminum plate. This indicates that current is flowing. The aluminum part may also bubble. Leave the power on until the part is slightly yellowed, the surface appears dull, and the bubbles have decreased in frequency. For small parts, this takes about two hours. Rinse the part in distilled water.
Mix dye and distilled water in a nonreactive pot. A stronger concentration of dye will yield a darker color. Place the part into the dye solution at room temperature, then heat the pot to 100 degrees Fahrenheit. Heat the aluminum part in the dye for 15 minutes. Boil a separate pot of distilled water. Rinse the part in cool water, then place it in the boiling water for 30 minutes. The boiling water bath seals the surface and completes the anodizing process.